Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.777384
Title: Breathing during sleep
Author: Douglas, Neil James
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2003
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Abstract:
This thesis reports studies on the cause, associations, diagnosis and treatment of breathing problems during sleep. The development of an accurate oximeter in the late 1970s allowed, for the first time, continuous measurement of oxygenation during sleep. Studies in patients with chronic obstructive pulmonary disease(COPD) demonstrated they became markedly hypoxaemic and hypoventilated during Rapid Eye Movement (REM) sleep. These episodes were associated with pulmonary hypertension and with raised erythropoetin and probably contribute to the development of cor pulmonale and secondary polycythemia. Subsequent studies showed no clinical value in performing overnight studies of breathing and oxygenation in routine practice. Having proved that patients with COPD had the same breathing pattern during sleep as normals, studies in normal subjects showed that ventilation and ventilatory responses to hypoxia and hypercapnia were decreased during sleep, most markedly during REM sleep. Modelling studies suggested hypoventilation could explain the sleep hypoxaemia in COPD. Studies in patients with asthma confirmed nocturnal symptoms were common and related to a sleep controlled circadian variation in airway calibre, at least partly due to variations in parasympathetic and non-adrenergic, non-cholinergic bronchomotor tone. It was also shown that changes in posture and in airway inflammation were not key to nocturnal asthma, and that consequences of nocturnal asthma included sleep disruption and cognitive impairment. Longacting inhaled (12 agonists were shown to improve asthma control and sleep quality. Having confirmed and extended the clinical features of the obstructive sleep apnoea/hypopnoea syndrome (OSAHS), studies were then performed to help clarify cause, associations, diagnosis and treatment of OSAHS. These identified a familial trait even in thin OSAHS patients and associated this with jaw shortening, and also identified gender, age and obesity related differences in upper airway structure and function. They also showed the importance of episodes of marked hypoventilation - hypopnoeas - in causing the syndrome, identified the neurocognitive consequences of OSAHS and showed that OSAHS was associated with elevation of blood pressure. They established that the symptoms and cognitive defects of OSAHS can be reproduced by repeated awakenings of normal subjects with sounds, and that even sounds which do not produce classical EEG arousals can produce sleepiness. Our investigations have also challenged the need to perform classical polysomnography to diagnose OSAHS, and helped establish that home sleep studies can be diagnostic in many patients, and are cost-effective. A series of randomised controlled trials of the CPAP therapy have provided a firm evidence base for the treatment of OSAHS. These have shown clear benefits from CPAP in terms of symptoms, sleep quality, objective sleepiness, cognition, quality of life, mood and blood pressure in symptomatic patients with >15 apnoeas + hypopnoeas/hr slept. In symptomatic patients with 5-15 apnoeas + hypopnoeas/hr slept there were definite benefits in symptoms, quality of life, mood and some areas of cognition but no change in objective sleepiness. These studies have been key to the current North American definitions of OSAHS. Studies also showed no benefit from treating asymptomatic individuals with >30 apnoeas + hypopnoeas/hr slept with CPAP. Our investigations have highlighted the need to monitor CPAP use, and shown that longterm CPAP use is >90% in sleepy patients with severe OSAHS. However milder patients use CPAP less well longterm, highlighting the need for effective alternative therapies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.Sc.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.777384  DOI: Not available
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